The present disclosure relates to calibration of optical sensors and, in particular, to a method and apparatus for providing multiple radiation spectra to an optical sensor for calibration purposes.
In various optical systems, an optical signal is received from an object at an optical sensor and measurements of the optical signal are obtained at the optical sensor to determine a property of the object. In order to obtain accurate measurements, it is often necessary to calibrate the optical sensor using a known photon flux at one or more standard wavelengths. One method for providing the photon flux at standard wavelengths includes heating one or more blackbody radiators to selected temperatures and using optical filters to select the wavelength. However, the use of blackbody sources to calibrate an optical sensor introduces size, weight, and power (SWaP) challenges. First of all, a conventional blackbody radiator needs to be heated for a relatively long time prior to use in calibration in order to bring the blackbody radiator to the selected temperature and to maintain the selected temperature. Conventional blackbody sources therefore consume a large amount of power. Secondly, conventional blackbody sources and their supporting optical structures are generally bulky, and using one or more of them requires a precise optical mechanism to image each blackbody emission spectrum onto the sensor undergoing calibration. Third, such a blackbody radiator calibration system and its accompanying optical mechanisms are generally heavy and cumbersome.